Agree. I'm not a LCD techwiz, I do know enough about basic Electronics to get by. Normally transistors (which is what makes a LCD work at its fundamentals) are either on or off. Either you're applying enough voltage to gate them, or you're not. Hell, without a back light, you can barely tell if a LCD is on. Some laptops can show you this if they have the ability to set the brightness to zero (which may not turn the backlight 'off'). Or to turn the backlight off, like on my Asus.

I dont see how it would be possible to leave a residual image even with a back light on. Unless, as was mentioned by another poster, the transistor got 'stuck' on.

That's exactly what he means. Being "stuck" is what he refers to. Each pixel is a set of RGB transistors. However, if a transistor is on for a long time, it can become stuck because the gate is worn out from constant current flowing. The Miller Effect, a capacitive characteristic between the drain and gate of a transistor (or collector and base, whatever kind of transistor you want to use as an example), can cause voltage problems because the voltage transients slow down, which results in slow pixels, or a burn-in.

At least, this is what I think the problem is. This is also a huge issue in why microchips can only go so fast, since the clock speed voltage is too slow and causes errors.